/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.phoenix.expression;

import java.math.BigDecimal;
import java.util.List;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.phoenix.exception.DataExceedsCapacityException;
import org.apache.phoenix.schema.SortOrder;
import org.apache.phoenix.schema.tuple.Tuple;
import org.apache.phoenix.schema.types.PDataType;
import org.apache.phoenix.schema.types.PDate;
import org.apache.phoenix.schema.types.PDecimal;
import org.apache.phoenix.util.NumberUtil;

/**
 * Subtract expression implementation
 * @since 0.1
 */
public class DecimalSubtractExpression extends SubtractExpression {
  private Integer maxLength;
  private Integer scale;

  public DecimalSubtractExpression() {
  }

  public DecimalSubtractExpression(List<Expression> children) {
    super(children);
    Expression firstChild = children.get(0);
    maxLength = getPrecision(firstChild);
    scale = getScale(firstChild);
    for (int i = 1; i < children.size(); i++) {
      Expression childExpr = children.get(i);
      maxLength = getPrecision(maxLength, getPrecision(childExpr), scale, getScale(childExpr));
      scale = getScale(maxLength, getPrecision(childExpr), scale, getScale(childExpr));
    }
  }

  @Override
  public boolean evaluate(Tuple tuple, ImmutableBytesWritable ptr) {
    BigDecimal result = null;
    for (int i = 0; i < children.size(); i++) {
      Expression childExpr = children.get(i);
      if (!childExpr.evaluate(tuple, ptr)) {
        return false;
      }
      if (ptr.getLength() == 0) {
        return true;
      }

      PDataType childType = childExpr.getDataType();
      boolean isDate = childType.isCoercibleTo(PDate.INSTANCE);
      SortOrder childSortOrder = childExpr.getSortOrder();
      BigDecimal bd = isDate
        ? BigDecimal.valueOf(childType.getCodec().decodeLong(ptr, childSortOrder))
        : (BigDecimal) PDecimal.INSTANCE.toObject(ptr, childType, childSortOrder);

      if (result == null) {
        result = bd;
      } else {
        result = result.subtract(bd);
        /*
         * Special case for date subtraction - note that only first two expression may be dates. We
         * need to convert the date to a unit of "days" because that's what sql expects.
         */
        if (isDate) {
          result = result.divide(BD_MILLIS_IN_DAY, PDataType.DEFAULT_MATH_CONTEXT);
        }
      }
    }
    if (maxLength != null || scale != null) {
      result = NumberUtil.setDecimalWidthAndScale(result, maxLength, scale);
    }
    if (result == null) {
      throw new DataExceedsCapacityException(PDecimal.INSTANCE, maxLength, scale, null);
    }
    ptr.set(PDecimal.INSTANCE.toBytes(result));
    return true;
  }

  @Override
  public PDataType getDataType() {
    return PDecimal.INSTANCE;
  }

  @Override
  public Integer getScale() {
    return scale;
  }

  @Override
  public Integer getMaxLength() {
    return maxLength;
  }

  @Override
  public ArithmeticExpression clone(List<Expression> children) {
    return new DecimalSubtractExpression(children);
  }
}
